Mode determination for mobile GPS terminals

ABSTRACT

The present invention discloses a system for determining the position of a GPS terminal. The system comprises a GPS terminal, a location aiding server, and a communications system. Messages are passed between the GPS terminal and the server, as well as within the GPS terminal, to determine the mode of operation of the GPS portion of the system. Decisions are made based on availability of aiding data and Quality of Service requirements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of U.S. patent Ser. No. 10/082,541,filed on Feb. 21, 2002, titled “MODE DETERMINATION FOR MOBILE GPSTERMINAL”, issued as U.S. Pat. No. 6,703,971 B2, that claims priorityunder 35 U.S.C. §119(e) of U.S. Provisional Patent Application No.60/270,682 filed on Feb. 21, 2001, titled “MODE DETERMINATION FOR MOBILEGPS TERMINAL,” by Ashutoshy Pande, et al., which are incorporated byreference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to Global Positioning System(GPS) mobile terminals, and in particular to methods and apparatuses fordetermining the mode of operation of a GPS receiver in a mobile terminalor device.

2. Description of the Related Art

Cellular telephony, including Personal Communication System (PCS)devices and other mobile terminals or devices, has become commonplace.The use of such devices to provide voice, data, and other services, suchas internet access, has provided many conveniences to cellular systemusers. Further, other wireless communications systems, such as two-waypaging, trunked radio, Specialized Mobile Radio (SMR) that is used bypolice, fire, and paramedic departments, have also become essential formobile communications.

A current thrust in the cellular and PCS arena is the integration ofGlobal Positioning System (GPS) technology into cellular telephonedevices and other wireless transceivers. For example, U.S. Pat. No.5,874,914, issued to Krasner, which is incorporated by reference herein,describes a method wherein the basestation (also known as the MobileTelephone Switching Office (MTSO)) transmits GPS satellite information,including Doppler information, to a remote unit using a cellular datalink, and computing pseudoranges to the in-view satellites withoutreceiving or using satellite ephemeris information.

This current interest in integrating GPS with cellular telephony stemsfrom a new Federal Communications Commission (FCC) requirement thatcellular telephones be locatable within 50 feet once an emergency call,such as a “911” call (also referred to as “Enhanced 911” or “E911”) isplaced by a given cellular telephone. Such position data assists police,paramedics, and other law enforcement and public service personnel, aswell as other agencies that may need or have legal rights to determinethe cellular telephone's position. Further, GPS data that is supplied tothe mobile telephone can be used by the mobile telephone user fordirections, latitude and longitude positions (locations or positions) ofother locations or other mobile telephones that the cellular user istrying to locate, determination of relative location of the cellularuser to other landmarks, directions for the cellular user via internetmaps or other GPS mapping techniques, etc. Such data can be of use forother than E911 calls, and would be very useful for cellular and PCSsubscribers.

However, cellular telephones are typically used in environments that aretypically not suitable for GPS signal reception, e.g., indoors, in urbanenvironments, or in tunnels or elevators. As such, there are manysituations where a cell phone that has an integrated GPS receiver cannotreceive GPS signals, because the cell phone is blocked from receivingsuch signals. Urban canyons, heavy foliage, or other scattering orblocking structures will prevent the receiver from getting theinformation it needs to determine the location of the cell phone. Thecellular system can then be used to deliver information to the GPSreceiver for the GPS receiver to perform the necessary calculations.

It can be seen that there is a need in the art for GPS enabled cellulartelephones. It can also be seen that there is a need in the art fordecision making intelligence accessible to the GPS receiver fordetermining whether the GPS receiver requires additional information inorder to make a position determination.

SUMMARY OF THE INVENTION

To minimize the limitations in the prior art described above, and tominimize other limitations that will become apparent upon reading andunderstanding the present specification, the present invention disclosesa system for determining the position of a GPS terminal.

In summary, the present invention discloses a system for determining theposition of a GPS terminal. The system comprises a GPS terminal, alocation aiding server, and a communications system. The GPS terminalincludes a GPS section for receiving and processing a GPS signal, and acall processing section, where a first message is passed from the callprocessing section to the GPS section via an interface between the GPSsection and the call processing section, and a second message is alsopassed via the interface from the GPS section to the call processingsection in response thereto. The first message comprises a Quality ofService (QoS) message and the second message comprises a QoS responsemessage.

An object of the present invention is to provide for GPS enabledcellular telephones. Another object of the present invention is toprovide a system that provides decision making intelligence accessibleto the GPS receiver for determining whether the GPS receiver requiresadditional information in order to make a position determination.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout:

FIG. 1 illustrates a typical GPS architecture as used in a cellularenvironment

FIG. 2 shows a typical interface between the Call Processing section andthe GPS section of the present invention; and

FIG. 3 illustrates the interface and GPS section operation utilizing thepresent invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following description of the preferred embodiment, reference ismade to the accompanying drawings which form a part hereof, and in whichis shown by way of illustration a specific embodiment in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention.

Overview

When integrating GPS components with wireless communications systems,the GPS system must have the capability to acquire and track the GPSsatellites under the conditions that the typical wireless communicationssystem user will encounter. Some of those conditions, e.g., indoor use,dense urban areas use that has a limited sky view, such as in downtownareas with skyscrapers blocking satellite views, etc., are possible withterrestrial-based wireless communications systems but present difficultsituations for GPS systems. Traditional standalone mode GPS, e.g., wherethe GPS receiver does not receive any outside assistance, has problemswith long Time To First Fix (TTFF) times, and also has limited abilityto acquire the GPS satellite signals under indoor or limited sky viewconditions. Even with some additional information, TTFF times can beover thirty seconds because ephemeris data must be acquired from the GPSsystem itself, and also requires a strong signal to acquire suchinformation reliably. These requirements of the GPS system have impactson the reliability of position availability as well as power consumptionin handheld GPS terminals.

Overview of the Present Invention

In the present invention, a server-client (or server-terminal)architecture is used. The terminal-side user has a GPS terminal, such asa cellular phone, and directly accesses to the terminal via a userinterface section of the terminal. The server-side user can access theserver via a user interface section of the server or from a userterminal via a network Accordingly, a positioning request from a userneeds to be received at both the terminal and the server. Furthermore,notice of a positioning result to a user needs to be made to both theterminal-side user and the server-side user.

GPS Architecture

FIG. 1 illustrates a typical GPS architecture as used in a cellularenvironment.

The wireless handset location technology of the present invention usesGPS technology in support of various wireless handset devices for theimplementation of E911 and geo-location services. By taking theadvantage of the low cost, low power, high performance and high accuracyGPS receivers enabled by the present invention, as well as the wirelessnetwork communication services, the wireless handset location technologyof the present invention provides highly reliable and economicalsolutions to the Wireless Aided GPS.

The wireless handset location technology of the present inventionsupports all kinds of geo-location services, from fully standalone mode,network aided mode, to network based service mode, to other modes. Thetechnology of the present invention also accommodates wide range ofwireless communication platforms, including CDMA, TDMA, AMP, and evenpager systems. FIG. 1 portrays the concept of wireless handset locationtechnology.

System 100 illustrates a GPS satellite 102, which is illustrative of theconstellation of GPS satellites 102 that are in orbit, a wireless GPSterminal 104 that comprises a GPS receiver, a base station 106, ageo-location (server) service center 108, a geo-location end application110, and a Public Safety Answering Point (PSAP) 112.

The GPS satellite 102 transmits spread spectrum signals 114 that arereceived at the wireless GPS terminal 104 and the geo-location server108. For ease of illustrative purposes, the other GPS satellites 102 arenot shown, however, other GPS satellites 102 also are transmittingsignals 114 that are received by the wireless GPS terminal 104 and thegeo-location server 108. If the wireless GPS terminal 104 can receive astrong enough signals 114, the GPS receiver in the wireless GPS terminal104 can compute the position of the wireless GPS terminal 104 as istypically done in the GPS system. However, wireless GPS terminals aretypically not able to receive strong enough signals 114, or are not ableto receive signals from enough GPS satellites 102 to autonomouslycompute the position of the wireless GPS terminal 104, but can stillcommunicate with the base station 106. Thus, the base station 106 cancommunicate information via signals 116 to the GPS terminal 104 to allowthe GPS terminal 104 to compute the location. If the basestation 106 istransferring information to the GPS terminal 104 to allow the GPSterminal 104 to compute position, it is called “wireless-aided GPS”.Furthermore, the basestation 106 can communicate aiding data from thegeolocation server 108 to the GPS terminal 104 to allow the GPS terminal104 to compute its position, or can communicate information from the GPSterminal 104 to the geo-location server 108 to allow the geo-locationserver 108 to compute the position of the GPS terminal 104. When thebasestation 106 transfers information from the geolocation server 108 tothe GPS terminal 104 it is called “network aiding GPS”, whereas when thebasestation 106 transfers information from the GPS terminal 104 to thegeo-location server 108 for the geo-location server 108 to compute theposition of the GPS terminal 104 it is called “network-centric GPS.”

The geolocation server 108 also communicates with the geolocation endapplication 110 via signals 118 and with PSAP 112 via signals 120. Thesesignals 118 and 120 can either be via wireless links or can be throughthe land line telephone network or other wire-based networks.

The wireless GPS terminal 104 location technology of the presentinvention comprises two major service systems: the wireless GPS terminal104 with the GPS receiver of the present invention and the geo-locationserver 108 containing the geo-location software modules of the presentinvention. In addition, there are two types of supporting systems: theBase Station (BS) 106 infrastructure, which provides the networkinformation transfer mechanism, and the PSAP 112 or the application 110system, which can initiate the geo-location network services.

FIG. 2 shows a typical interface between a Call Processing section andthe GPS section of the present invention.

As shown in FIG. 2, the GPS terminal 104 comprises a Call Processing(CP) section 200 and a Global Positioning System (GPS) section 202.Within the GPS terminal 104, or, alternatively, between the GPS terminal104 and an external accessory to the GPS terminal 104, communicationsbetween the CP section 200 and the GPS section 202 take place. Thesecommunications allow signals to be transferred from CP section 200 toGPS section 202, and typically take place on a serial communicationslink 204 and hardware lines 206, but other connections can be used ifdesired.

For example, in another implementation, the CP section 200 and the GPSsection 202 can share the same digital processor and other circuitry. Insuch a case, the communication between sections can be made byinter-task communication, and certain data transfers, such as any timeor frequency transfers between the CP section 200 and the GPS section202, would not use the hardware lines 206, but would be internal to thecircuitry or, potentially, no transfer would be required depending onthe circuit design.

The GPS section 202, also known as the SiRFLoc Client (SLC) can beoperated in at least two modes: a Call Processing centric (CP centric)mode or a SiRFLoc Server (SLS) centric mode. Typically, the mode isdetermined by the internal information available to the GPS section 202.Normally, the GPS section is started in the CP centric mode, but can bestarted in the SLS centric mode if desired. In the SLC centric mode, theGPS terminal 104 is operated in a standalone mode without any networkconnection. The GPS section 202, once in the SLS centric mode, relies onthe SLS server, also known as the Geolocation service center 108 or PSAP112, to provide network aided data for position computation by the GPSsection 202. Once in the SLC centric mode, there is typically no returnto the CP centric mode unless conditions change or the call processor200 determines that the mode of the GPS section needs to be changed.

In addition to the SLC modification for CP centric operation, theair-interface protocol for the GPS terminal 104 is typically modified tooptimize the message exchange between the geolocation service center 108and the GPS terminal 104, to reduce message traffic over the network andto reduce the overall Time To First Fix (TTFF) for GPS terminal 104.

The present invention allows the GPS section 202 to provide position andsatellite information to the call processor 200 in either NMEA or otherformat (typically binary messages, such that the call processor is ableto determine which mode the GPS section 202 is operating in, or,potentially, to override the mode of operation of the GPS section 202.This allows the GPS section 202 to communicate with the call processor200 information other than a determined position, in order for the callprocessor to meet Quality of Service (QoS) requirements, TTFFrequirements, cost savings, or other programmed parameters that can beuser selected or pre-programmed into the GPS terminal 104.

Interface and GPS Section Operation

FIG. 3 illustrates the interface and GPS Section operation utilizing thepresent invention.

Serial communications lines 204 and hardware lines 206 are shownconnected to GPS section 202. Message 300 is passed to the processingsection 302 of GPS section 202. Message 300 comprises a Quality ofService (QoS) request to GPS section 202, which tells GPS section 202the time and position accuracy required by the call processing section200 for the position data to be determined by the GPS section 202.Processing section 302 is also in communication with GPS receiver 304via link 306, and, as such, processing section 302 knows or cancalculate how long it will take GPS receiver 304 to determine a positionof GPS terminal 104. Message 300 is issued by the call processor 200 asneeded.

In response to the message 300 (the QoS request), the GPS section 202,after calculating or determining whether the time and accuracyrequirements of message 300 can be met by GPS section 202, respond tothe call processor 200 via message 308. Message 308 is reported to thecall processor 200 via serial communications lines 24 or hardware lines206, or both, as needed.

Message 308 can have several forms. The message 308 can be that the QoSrequested, i.e., the position accuracy and TTFF requested by callprocessor 200, can be obtained by GPS section 202. As such, the CPcentric mode for the GPS section 202 will be continued so long as thecall processor 200 or the geolocation service center 108 does not changethe mode of the GPS section 202.

The message 308 can also report that the position accuracy requested inmessage 300 cannot be obtained within the TTFF requested, but can beobtained eventually in a longer time period. Typically, the callprocessor 200 will determine whether to allow GPS section 202 tocontinue operating in CP centric mode, or to switch the GPS section 200to SLS centric mode, but GPS section 202, in some embodiments, can makethis determination by itself without resorting to the call processor200.

Message 308 can also report that GPS section 202 cannot obtain theposition accuracy, or potentially, no position determination at all,even after an extended period of time. If such a message 308 isdetermined, either the call processor 200 will switch GPS section 202into the SIS centric mode, or the GPS section 202 will automaticallyswitch to the SLS centric mode of operation.

Message 308 can also contain flags for aiding parameters expected ordesired from geolocation service center 108, e.g., whether GPS section202 requires time, frequency, approximate location, or ephemeris data,or any combination thereof. Each flag within message 308 would be set toa true value if that aiding parameter is required or desired by the GPSsection 202, otherwise, the flag would be set to a false value. The GPSsection 202 may issue the QoS response message 308 as needed once itreceived the first QoS request message 300 from the call processor 200.

The processor 302 determines the QoS Strategy of the GPS section 202. Assuch, the processor 302 determines what information it may need prior toposition determination, or, even during position determination after aQoS message 300 request. The QoS strategy is determined by the presenceor absence of satellite signals, e.g., the number of satellites fromwhich signals are being received, a frequency range used for searchingfor satellites, a time range used for searching for satellites, and acurrent searching status of the GPS section 202, as well as otherfactors.

As such, the processor 302 initializes the GPS section 202 withinformation received from the call processor 200. The processor 302section of the GPS section 202 requests information from the callprocessor, e.g., hardware configuration information, etc., as well asapproximate GPS mobile terminal 104 position, from the call processor200. Call processor 200 either sends a stored mobile terminal 104position to the GPS section 202 if such a stored position is available,or, if there is no stored information available, the call processorsends a “reject” message or a “data not available” message.

The call processor 200 then sends a session open request to the GPSsection 202 to start a position determination in a GPS standalone mode,ie., where there are no aids or assist messages to the GPS section 202for position determination. After the GPS section 202 has started toreceive GPS signals from GPS satellites 102 and potentially starteddetermining the position of mobile terminal 104, the call processor 200sends message 300 to GPS section 202 to determine the QoS that the GPSsection 202 can meet. If the standard QoS message 300 request cannot bemet by GPS section 202, either processor 300 or call processor 200 candetermine, based on the content of message 308, whether the QoS that canbe delivered by GPS section 202 is acceptable. Otherwise, either callprocessor 200 or processor 302 can change the mode of operation of GPSsection 202 to another mode to be able to deliver the desired QoS. Thecall processor 200 sends message 300 to GPS section whether or not theposition determination being performed by GPS section 202 is completedor not. Although GPS section 202 may receive message 300 during or afteracquisition of GPS satellites 102, call processor 200 mayor may notreceive message 308 before a position determination has been made by GPSsection 202.

The starting mode for GPS section 202 is determined based on theinformation obtained from stored information, e.g., information storedin RAM or the known accuracy of clocks used by the GPS section 202, aswell as any initial information received from the call processor 200 orthe geolocation service center 108. The GPS section 202 then can computewhat aiding data, if any, is needed, as well as having the capabilityfor reporting QoS capabilities of GPS section 202 to call processor 200.Table 1 illustrates what data is used to determine the startup mode forGPS section 202.

TABLE 1 Start up mode determination Battery Backed Up RAM Snap Hot WarmCold Parameters Start Start Start Start Time T < 3 min X T > 3 min X XValid Location X X X Valid Ephemeris < 2 hrs X X Valid SV State Table XAny parameter is not valid X (invalid checksum in RAM, Ephemeris > 2hrs)Acquisition State

At the beginning of the Acquisition of GPS satellites 102, the GPSsection 202 sends message 308 to call processor 200. During this stateof acquisition of GPS satellites, GPS section 202 is typically in the CPcentric mode, following a CP centric strategy algorithm determined bythe GPS section 202. At the end of the acquisition state of the GPSsection 202, GPS section 202 will have additional information regardingwhether aiding information is required from either the call processor200 or the geolocation service center 108, and what, if any, types ofaiding information is required.

Tracking State

When GPS section 202 is tracking GPS satellites 102, i.e., when asatellite 102 signal 114 has been received and the data from the signalhas been retrieved, GPS section 202 can determine whether the message308 previously sent during acquisition state is still valid, or ifanother message 308 needs to be sent to update the QoS available fromthe GPS section 202. For example, if GPS section 202 has only acquiredone or two GPS satellites 102, and is tracking those GPS satellites 102then GPS section 202 may not have enough information to determine aposition for mobile terminal 104. While in tracking mode, the GPSsection will continue to run the CP centric strategy unless networkaiding is required. If the system ever switches to SLS centric mode,either the geolocation service center 108 or the GPS section 202 cancalculate the position of the mobile terminal 104.

NMEA/SiRF Binary Interface

As part of the features specific for the present invention, the GPSsection 202 can also provide a minimum set of data listed in NMEASpecification 0183, version 2.1 dated Oct. 14, 1995, which isincorporated by reference herein, and can supply other binary messagesto the CP in parallel to the standard interface with the call processor200. Such an interface is shown as interface 310, although the interfacecan also be through serial interface 204 or hardware interface 206 asdesired. Further, any interfaces to the call processor 200 can bedirectly to the GPS receiver 304 through links 312 and 314 if desired.

Typically, interface 310 is on a separate port, (Port B), with a baudrate of 100 bits per second (bps) or higher, with the following NMEAmessages:

GGA: user position data—time, position (longitude, latitude) and fixrelated data.

VTG: Course Over Ground (COG) and Speed Over Ground (SOG).

GSV: SV in view—number of SVs, elevation, azimuth and SNR.

GSA: GPS DOP and active SV—GPS operating mode, SV used in NAV solutionand DOP (PDOP, HDOP, VDOP) values.

Some proprietary messages, typically sent in binary format, are asfollows:

Measured Navigation Data Message (message ID #2): handset positioninformation and quality indicators (similar to GGA and VTG of NMEA).

Measured Tracker Data Message (message ID #4): GPS time, number of SVs,azimuth, elevation, tracking state C/NO (similar to GSV of NMEA)

Operation

Typically, the call processor 202 sends to GPS section 202 a binary(possibly a proprietary binary message to enable the message via link310. Such a message 316 will be output at a specified baud rate. Thecall processor 200 can send this message to the GPS section 202 atanytime, or as needed, to switch from one message type to another, or toenable or disable the link 310. When GPS section 202 computes aposition, GPS section 202 sends a message 316, either an NMEA or binarymessage to the call processor 200 via port 310. The GPS section 202 alsosends a GSA message described above if the NMEA message 316 is used.

Over-the-Air Message Regrouping

Similarly, a message from the geolocation service center 108 can begrouped into the message being sent from the call processor 200 to theGPS section 202 on port 310 if desired. The GPS section 202 can send anaiding data request message 310 or message 308 to specify what kind ofaiding data is requested from the geolocation service center 108. Eachdata aiding message from geolocation service center 108 typicallycontains only one kind of aiding information, but can contain more ifdesired.

Conclusion

This concludes the description of the preferred embodiment of theinvention The following paragraphs describe some alternative methods ofaccomplishing the same objects. The present invention, althoughdescribed with respect to GPS systems, can be utilized with anySatellite Positioning System (SATPS) without departing from the scope ofthe present invention.

In summary, the present invention discloses a system for determining theposition of a GPS terminal. The system comprises a GPS terminal, alocation aiding server, and a communications system The GPS terminalincludes a GPS section for receiving and processing a GPS signal, and acall processing section, where a first message is passed from the callprocessing section to the GPS section via an interface between the GPSsection and the call processing section, and a second message is alsopassed via the interface from the GPS section to the call processingsection in response thereto. The first message comprises a Quality ofService (QoS) message and the second message comprises a QoS responsemessage.

The communication system, selectively transmits first data to the GPSterminal from the location aiding server and receives data from the GPSterminal to send to the location aiding server, based on the firstmessage and the second message.

The foregoing description of the preferred embodiment of the inventionhas been presented for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the invention to theprecise form disclosed. Many modifications and variations are possiblein light of the above teaching. It is intended that the scope of theinvention not be limited by this detailed description, but rather by theclaims appended hereto.

1. A Global Positioning System (GPS)-based positioning system,comprising: a GPS terminal, including: a GPS section for receiving andprocessing a GPS signal; a call processing section, coupled to the GPSsection via an interface, a first message being passed from the callprocessing section to the GPS section via the interface, and a secondmessage is passed via the interface from the GPS section to the callprocessing section in response thereto, wherein the first message is aQuality of Service (QoS) message and the second message is a QoSresponse message; and a communication system capable of communicationwith a location aiding server, coupled to the GPS section and the callprocessing section, for selectively transmitting first data to the GPSterminal from the location aiding server and receiving data from the GPSterminal to be sent to the location aiding server, based on the firstmessage and the second message if the QoS response message indicatesthat first data is required by the GPS section in order to provide apredetermined QoS, otherwise no location aiding data is employed.
 2. Thesystem of claim 1, wherein the location aiding server calculates aposition of the GPS terminal based upon data received from the GPSterminal.
 3. The system of claim 2, wherein the GPS section furthercomprises a processor separate from the call processor.
 4. The system ofclaim 3, wherein the call processor uses a predetermined strategy todetermine content of the second message.
 5. The system of claim 4,wherein the predetermined strategy employed by the call processor of theGPS section is determined by at least one parameter selected from agroup comprising: a signal level of received satellite signals, a numberof satellites from which signals are being received, a frequency rangeused for searching for satellites, a time range used for searching forsatellites, and a current searching status of the GPS section.
 6. Thesystem of claim 5, wherein the second message comprises a messageindicating that a QoS request can be met by the GPS section.
 7. Thesystem of claim 5, wherein the second message comprises a messageindicating that a QoS request can not be obtained by the GPS section andcan be obtained if additional time is granted by the call processor. 8.The system of claim 7, wherein the call processor switches anoperational mode of the GPS section in response to the second message.9. The system of claim 7, wherein the GPS section switches anoperational mode of the GPS section based on content of the secondmessage.
 10. The system of claim 7, wherein the location aiding serversends aiding data to the GPS section.
 11. The system of claim 5, whereinthe second message comprises a message indicating that a QoS requestcannot be obtained by the GPS section.
 12. The system of claim 11,wherein the call processor switches an operational mode of the GPSsection in response to the second message.
 13. The system of claim 11,wherein the GPS section switches an operational mode of the GPS sectionbased on content of the second message.
 14. The system of claim 11,wherein the location aiding server sends aiding data to the GPS section.